The present invention relates to a method for the compression of pulses, notably in microwave transmission.
It can be applied notably to radars for the detection of furtive or stealthy targets. More generally, it can be applied to all radars whose function requires the transmission of high peak power during very brief pulses.
To combat stealthy targets for example, it is necessary to send out pulses that have a shorter duration than the reaction times of these stealthy targets, which are themselves very brief. It is then necessary, for example, to compress the pulses sent by a ratio of about 10, at constant mean transmitted power. This may lead to the compression, for example, of pulses with a duration of 100 ns at 1 MW peak power into pulses with a duration of about 10 ns at 10 MW peak power.
The analog compression of frequency modulated pulses is a well known technique used at reception. Compression at transmission and at high levels of power has already been achieved. One device has notably been described in the article by Z. D. Farkas, H. A. Hogg, G. A. Loew and P. B. Wilson, "SLED: A Method Of Doubling SLAC's Energy", Stanford Linear Accelerator Center, Stanford University, 1974. The device described uses the time taken for the filling of a resonant cavity as the delay between the front edge of the pulse and the rear edge. This method is limited by the overvoltages due to the resonance, by the losses in the cavity and by the strong electrical fields proportional to the overvoltage of the cavity.
Owing to the limited gain of this structure, another device called a "Binary Power Compressor" has been designed. This device is described in the article by Z. Farkas, "Binary Peak Power Multiplier And Its Application To Linear Accelerator Design", IEEE Trans MTT 34--1986, page 1036. It uses two parallel amplification channels, one of the channels being delayed with respect to the other one before their recombination in phase and before the reduction, by a factor of two, of the pulse duration.
To achieve a substantial reduction in the duration of the pulses, it is therefore necessary to use a large number of sections of this type, which complicates the device and makes it bulky and costly.